For many companies, the amount of time, money and people required to manage components in a data center has made managing service availability more difficult. Commodity hardware and virtualization technologies using data center virtualization attempt to reduce traditional energy requirements. Data center virtualization is the process of aligning resources with the needs of services. Virtualization technology enables creation of a set of logical resources that share underlying physical resources. A group of resources, such as servers, applications, databases, and networks, behave as a single resource from which all services are drawn. It requires application components, access software, virtualized operating systems, storage, etc. A key challenge to this has been provisioning and managing these complex environments to ensure cost-effective, efficient service.